Like July in January, New York City electricity prices surged to record highs last month, causing many Con Ed customers’ bills to spike more than 20 percent.

The utility blames the boost on rising prices for natural gas, which powers most electricity generators. Natural-gas prices rose because the cold weather drove up demand for gas heat.

“It’s astronomical!” said Jerilynn Mabry of Harlem, who complained to the AARP, which is lobbying for better regulation of the state’s utility industry.

Mabry’s bill for January was $87.36, a 17 percent jump from her December bill of $74.74. “Usually, my winter bills are much less — $46, $36,” said Mabry, a 64-year-old retiree. “It’s amazing this year.”

Leigh Jones, another Harlem resident, saw her bill jump from $60 for December to $101 for January. “I was definitely surprised,” said the 40-year-old college professor.

Jones says Con Ed wrongly claims she increased her electricity use. But she noticed in the January bill’s fine print she’s paying a supply charge of 18.8 cents per kilowatt hour, far higher than usual for this time of year.

The supply charge, which covers the cost of actually generating electricity, is the source of this winter’s power-bill misery.

Con Edison’s electricity supply charges are adjusted daily, the company says. The number that shows up in bills is an average of the daily prices.

A Con Ed customer with a billing period from Dec. 30 to Jan. 30 paid an average supply charge for the month of 23.1 cents per kilowatt hour — a shocking 83 percent boost over the 12.6-cent charge during the same period last year.

That price is the highest in at least five years and even tops the price spikes Con Edison customers see in the summer air-conditioning season.

The company says a typical New York City customer’s January bill for 300 kilowatt hours was $118, a boost of $21, or 22 percent, over last year.

Con Ed does not control the price of electric generation and says it passes on generating companies’ charges without markup.

Despite Gov. Cuomo’s blocking of hydraulic fracking upstate, fracking in Pennsylvania and West Virginia has made natural gas used to heat buildings and generate electricity far cheaper and more abundant in the Northeast.

But the demand for gas heat this winter has stressed gas-delivery pipelines, federal energy watchers say. Even though several new pipelines are serving the city this winter, “natural-gas supply into the New York region remains constrained during high-demand periods,” the US Energy Information Administration reports.

It didn’t help that one of the two Indian Point nukes went off-line on Jan. 6 when a water-flow controller failed.

The plant was off the power grid for two days — and during that time, government data shows, the price of electricity New York utility companies buy at auction more than doubled.

Entergy, Indian Point’s owner, says New York’s electricity price spike shows the need for the plant, which Cuomo wants to shut down over safety fears.

“Indian Point provides protection against even more volatile price increases,” said Entergy spokesman Jerry Nappi.

This winter’s power price surge adds to the pain Con Ed customers already suffer by paying what federal data show are the highest electricity prices charged by a major US utility.